This prosthesis (1), comprises an expandable tubular frame (2) with a mesh structure and a prosthetic valve (3) mounted on this framethe ventricular portion (2v) of the frame (2) has a large indentation (6) on one side, extending lengthwise from the end of this ventricular portion (2v) that is opposite said annular portion (2i) to the part of this ventricular portion (2v) close to the annular portion (2i), this indentation (6) extending over a sector of the circumference of the prosthesis (1) of about 90 to 140°said atrial portion (2a) flares toward the outside of the prosthesis, from said annular portion (2i) toward the end of this atrial portion opposite this annular portion, and comprises anchoring spikes (5a) on the side of said annular portion (2i) andsaid ventricular portion (2v) has a substantially spherical or ovoid shape and comprises anchoring spikes (5v) on the side of said annular portion (2i).
